Microdeletions and microduplications are recurrent
in the q11.2 region of chromosome 22. The 22q11.2
duplication syndrome is an extremely variable disorder
with a phenotype ranging from severe intellectual disability,
facial dysmorphism, heart defects, and urogenital
abnormalities to very mild symptoms. Both benign and
malignant hematological entities are rare. A male patient
was diagnosed with mild facial dysmorphia, congenital
heart anomalies shortly after birth and acute bowel obstruction
due to malrotation of the intestine at the age of
3 years. A whole-genome single nucleotide polymorphism
(SNP) array revealed a de novo 6.6 Mb duplication in
the 22q11.1q11.22 chromosomal region. A year later, the
patient was diagnosed with acute pre-B lymphoblastic
leukemia (pre-B ALL). Five genes, CDC45, CLTCL1,
DGCR2, GP1BB and SEPT5, in the 22q11.1q11.22 region
are potentially responsible for cell cycle division. We hypothesized
that dosage imbalance of genes implicated in
the rearrangement could have disrupted the balance between
cell growth and differentiation and played a role in
the initiation of malignancy with a hyperdiploid leukemic
clone, whereas over-expression of the TBX1 gene might
have been responsible for congenital heart defects and
mild facial dysmorphia.